green build up on tongue

Hi, ive had a problem with a greenish build up on my tongue for several years now but have been putting it off. I have researched on the internet and seen symptoms of white tongues or furry tongues but mine is a greenish colour. Every night i use a scraper to remove it from tongue and it seems to look a normal color after this but by the next night it is back again. Sometimes there is only a small amount but then other days there is a large amount of it. It is begining to annoy me now and i want to do something about it. Thank you.